import java.util.Arrays;

/**
 * @Author 12629
 * @Description：
 */
public class TestHeap {

    public int[] elem;
    public int usedSize;

    public TestHeap() {
        this.elem = new int[10];
    }


    //创建一个大根堆  时间复杂度O(N)
    public void createHeap(int[] array) {
        for (int i = 0; i < array.length; i++) {
            elem[i] = array[i];
            usedSize++;
        }
        //把原始数据 给到了 elem数组
        for (int parent = (usedSize-1-1)/2; parent >= 0 ; parent--) {
            shiftDown(parent,usedSize);
        }
    }

    /**
     *
     * @param parent 每棵子树的根节点
     * @param len 代表每棵子树的结束位置
     */
    private void shiftDown(int parent,int len) {
        int child = 2 * parent+1;
        //是不是一定有左孩子
        while (child < len) {
            //一定 不会越界 ！！！！
            if(child + 1 < len && elem[child] < elem[child+1]) {
                child = child + 1;
            }
            if(elem[child] > elem[parent]) {
                int tmp = elem[child];
                elem[child] = elem[parent];
                elem[parent] = tmp;
                parent = child;
                child = 2 * parent+1;
            }else {
                //此时本身 就是一个大根堆
                break;
            }
        }
    }


    public void push(int val) {
        //1. 检查满
        if(isFull()) {
            elem = Arrays.copyOf(elem,2*elem.length);
        }
        //2、存数据
        elem[usedSize] = val;
        usedSize++;
        shiftUp(usedSize-1);
    }


    public boolean isFull() {
        return usedSize == elem.length;
    }

    public void shiftUp(int child) {
        int parent = (child-1)/2;
        while (child > 0) {
            if(elem[child] > elem[parent]) {
                int tmp = elem[child];
                elem[child] = elem[parent];
                elem[parent] = tmp;
                child = parent;
                parent = (child-1)/2;
            }else {
                break;
            }
        }
    }

    public void poll() {
        if(empty()) {
           throw new HeapEmptyException("优先级队列是空的！");
        }
        int tmp = elem[0];
        elem[0] = elem[usedSize-1];
        elem[usedSize-1] = tmp;
        usedSize--;//9
        shiftDown(0,usedSize);
    }

    public boolean empty() {
        return usedSize == 0;
    }

    public int peek() {
        if(empty()) {
            throw new HeapEmptyException("优先级队列是空的！");
        }
        return elem[0];
    }

    /**
     *  1. 建立大根堆：O(n)
     *  2. N*logN
     */
    public void heapSort() {
        int end = usedSize-1;
        while (end > 0) {
            int tmp = elem[0];
            elem[0] = elem[end];
            elem[end] = tmp;
            shiftDown(0,end);
            end--;
        }
    }
}
